Palm oil mill effluent (POME) is a high strength agro-industrial wastewater that contains

significant amount of organic suspended solids. These solids reduce plant efficiency and account for

additional maintenance of fixed bed digesters. An anaerobic fluidized bed reactor was studied to evaluate

the performance of the system to treat solids from the POME. The hydraulic retention time (HRT) was

reduced step wise from 24 hr to 4 hr, which resulted in volumetric loading rates of 4.0 kg COD/m3.d to 13.8

kg COD/m3.d, respectively. The maximum TSS removal rates varied in the range of 68% - 89%. The AFBR

showed promising performance without exhibiting any problem pertaining to the solids in the wastewater.

The AFBR exhibited low sludge production with sludge volume indices (SVI) of between 11 L/mg and 35

L/mg. The low SVI indicates fast settleability and self-compressibility of the digested solid particles in

POME. The study showed the superiority of AFBR over the other treatment processes in treating industrial

wastewater that contains significant portion of solids

Idris, Azni

Mamun, Abdullah Al

The International Islamic University Malaysia Repository

Asian Jr. of Microbiol. Biotech. Env. Sc. Vol. 23, No. (1) : 2021 : 102-105© Global Science PublicationsISSN-0972-3005ANAEROBIC FLUIDIZED BED REACTOR (AFBR) FOR THETREATMENT OF HIGH SOLID CONTENT AGRO-INDUSTRIALWASTEWATERABDULLAH AL-MAMUN1* AND AZNI BIN IDRIS21 Department of Civil Engineering, Kulliah of Engineering, International Islamic University Malaysia(IIUM), Jalan Gombak, 53100 Kuala Lumpur, Malaysia2 Department of Chemical and Environmental Engineering, Universiti Putra Malaysia 43400, UPMSerdang, Selangor, Malaysia(Received 10 December, 2020; Accepted 8 January, 2021)Key words : Anaerobic Fluidized Bed Reactor, Agro-industrial wastewater, Wastewater treatmentAbstract – Palm oil mill effluent (POME) is a high strength agro-industrial wastewater that containssignificant amount of organic suspended solids. These solids reduce plant efficiency and account foradditional maintenance of fixed bed digesters.  An anaerobic fluidized bed reactor was studied to evaluatethe performance of the system to treat solids from the POME. The hydraulic retention time (HRT) wasreduced step wise from 24 hr to 4 hr, which resulted in volumetric loading rates of 4.0 kg COD/m3.d to 13.8kg COD/m3.d, respectively.  The maximum TSS removal rates varied in the range of 68% - 89%. The AFBRshowed promising performance without exhibiting any problem pertaining to the solids in the wastewater.The AFBR exhibited low sludge production with sludge volume indices (SVI) of between 11 L/mg and 35L/mg. The low SVI indicates fast settleability and self-compressibility of the digested solid particles inPOME. The study showed the superiority of AFBR over the other treatment processes in treating industrialwastewater that contains significant portion of solids.INTRODUCTIONDepending on the effluent characteristics, industrialwastewaters are treated by physical, chemical andbiological unit processes (Qasim, 1999; Ma, 1992;Tchobanoglous and Burton, 1991; Sutton andMishra, 1990).  Generally, combinations of two ormore unit processes are required to achieve asatisfactory level of removal efficiency.  Anaerobicbiological treatment is widely accepted in the agro-industries, mainly due to less energy requirement,capability to handle high pollution loading rate,production of bio-gas as by-product, etc. (Mathiot etal., 1992).Most of the palm oil industries in Malaysia useconventional, land consuming and inefficient pondtreatment system (Ma et al., 1993).  The pondsystems are designed depending on few parameters,such as hydraulic retention time (HRT), solidsresidence time (SRT), influent and effluentconcentrations, sludge age, etc.  Most of these pondsare anaerobic and others are either facultative oraerobic. Large surface areas are required to treat thewastewater satisfactorily, with classical pondsystems.  These systems are unable to treat thewastewaters to the satisfactory level and thuspartially treated effluent from the ponds addspollutants to the surface waters.  Lately few types ofclosed tank anaerobic digesters are being installed insome of the big industries.  One of the majorproblems with other treatment system is to handlethe solids available in POME.  Thus, there was aneed to find out a suitable treatment system, whichis cheaper but efficient and can tackle the problem ofhaving solids in the wastewaters.Up-flow anaerobic sludge blanket, anaerobicfilters, anaerobic expanded bed reactor andanaerobic fluidised bed reactor are mostly preferredfor high strength wastewater treatment (Idris, 1993).AFBR provides longer solid residence time (SRT),which is required for efficient and stable operationof the system.  Higher SRT and shorter HRT are theimportant prerequisites for an economical treatmentsystem (Switzenbaum, 1983). Recently, palm oilAnaerobic Fluidized Bed Reactor (AFBR) for the Treatment of High Solid Content Agro- 103industries in Malaysia are introducing anaerobicdigesters into their treatment facilities, but no AFBRis, so far, reported to be installed in any industry.Besides, no large-scale study is undertaken so far toevaluate the feasibility of anaerobic fluidized bedreactors for the treatment of palm oil mill effluent(POME), let alone full-scale implementation. Themain objective of this paper is to report theperformance of an AFBR for the treatment ofindustrial wastewater in the context of suspendedsolid removal performance.METHODOLOGYThe AFBR (Figure 1) was partially filled with sand,having uniformity coefficient (Cu) of 1.6 andgradation coefficient (Cc) of 1.09.  The concentratedPOME was diluted to provide uniform organic loadranging between 1.8 and 2.0 kg COD/m3.day duringthe start-up period.  As BOD does not represent thetotal organic content in the substrate (Orhon et al.,1998), the chemical oxygen demand (COD) wasmonitored to define steady states and to determinethe kinetic coefficients.It was assumed that the system had attainedsteady state when difference among COD removalrates for three consecutive tests varied within 5 %.The substrate (POME) consisted of about 90-95 % ofwater, 4.5-9 % of solids (approximately half insolution and the rest in suspension), and 0.5-1 %residual and grease.  Palm oil mill effluent (POME)has very high BOD (25,000-30,000 mg/L) and COD(50,000-60,000 mg/l). The reactor was operatedunder ambient temperature ranging between 25-31oC (mesophilic condition) with pH around 7.  Thesamples were collected daily and analysedaccording to Standard Methods (APHA, 2005). RESULTS AND DISCUSSIONAccording to Hobson and Wheatly (1993) mostdigester systems are self-buffering at around pH 7.Therefore, pH of the pilot plant AFBR wasmaintained around 7. Chemical oxygen demand(COD) was considered as the main controllingparameter to define steady states and overall reactorperformance.  COD was monitored almost daily andthe plot (Figure 2) was more representative to thedigester activity.  The Maximum COD removal rateachieved at steady state was 85% and the minimumwas 65.2% (Figure 2).  These were achieved at HRTof 12 and 4 hour under OLR of 4.0 and 13.8 kg COD/m3.d, respectively.  Figure 3 shows the COD removalplotted against loading rate. The result showed that,COD removal rate decreased steadily withincreasing loading rate. This observation was inagreement with the trend reported by Chen et al.(1985).Figure 2 shows the reactor performance in termsof total suspended solids (TSS) removal. TSSremoval rate throughout the study was promising.Maximum TSS removal rate achieved was 89% at anHRT of 12 hour. This removal rate was achieved atan OLR of 1.92 kg TSS/m3.d.  TSS removal efficiencywas declining with the increase in OLR but thedecrement was less at loading rates higher than 4kgTSS/m3.d. Despite promising settlingcharacteristic of the effluent, there was always somepermanent colour in the treated effluent.  Kutty et al.(2019); Chaijak et al. (2017); Ng (2016) and Neoh et al.(2013) also observed similar problems of havingcolour in POME.  This colour could not be removedFig. 1. The anaerobic fluidised bed reactor (AFBR) and the wastewater (POME)(a) AFBR (b) Raw, Treated and Settled POME104 ABDULLAH AL-MAMUN AND AZNI BIN IDRISsubstantially even by ultra-membrane filtrationWong et al. (2002) and Khor (1998).CONCLUSIONA pilot scale anaerobic fluidised bed reactor (AFBR)was studied for treatment of agro-industrialwastewater, which was diluted palm oil mill effluent(POME) that contains significant amount of solids.Special attention was given to evaluate theperformance of the reactor in removal of solids.Chemical oxygen demand (COD) of the substratewas considered as the main monitoring parameterto define the steady states and overall reactorperformance.  The COD loading rates were variedbetween 4 and 13.8 kg COD/m3.d.  The minimumand maximum TSS removal rates were 68% and 89%at hydraulic retention time (HRT) of 4 and 12 hours,respectively. The system ran well without anyclogging problems. The study showed that theAFBR has the potentiality to treat industrialwastewater that contains significant portion ofcoarse and fine organic solids.REFERENCESAPHA, 2005. Standard Methods for the Examination of Waterand Wastewater. 21st edition. American Public HealthAssociation, Washington DC, the USA.Chaijak, P., Lertworapreecha, M. and Sukkasem, C. 2017.Decolorization and phenol removal of palm oil milleffluent by termite-associated yeast. In InternationalConference on Pollution Control and Waste Management,UAE, Dubai, 30–31.Chen, S.J., Li, C.T. and Snieh, W.K. 1985. Evaluation of theanaerobic fluidised bed system: biomass hold-up andcharacteristics. J. Chem. Tech. Biotechnol. 35B:183-190.Hobson, P.N. and Wheatley, A.P. 1993. Anaerobic Digestion.London: Elsevier Applied Science, Essex, UK.Fig. 2. Performance of the AFBR in removing COD and TSS from wastewaterIdris, A. 1993. Fixed film process and scale-up aspects inanaerobic systems. In : Proceeding Biological Processesin Pollution Control, Kuala Lumpur, 83-88.Khor, O.Y. 1998. Kenetic study of anaerobic digestion withbiomass retention by ultrafiltration membranes. M.S.thesis, Universiti Putra Malaysia, Selangor, Malaysia.Kutty, S.R.M., Almahbashi, N.M.Y., Nazrin, A.A.M., Malek,M.A., Noor, A., Baloo, L. and Ghaleb, A.A.S. 2019.Adsorption kinetics of colour removal from palm oilmill effluent using wastewater sludge carbon incolumn studies. Heliyon. 5 : e02439.Ma, A.N. 1992. Current status and future trends in theenvironmental management of palm oil industry. In: Seminar on municipal and industrial waste managementtechnology, 18-19 February, 1992. Kuala Lumpur.Ma, A.N., Cheah, S.C. and Chow, M.C. 1993. Current statusof palm oil processing wastes management. In Yeoh,B.G., Chee, K.S, Phang, S.M., Isa, Z., Idris, A. andMohamed, M. (ed.) Waste Management in Malaysia:Current Status and Prospects for Bioremediation, KualaLumpur: 111-136.Mathiot, S., Escoffier, Y., Ehlinger, F., Couderc, J.P. andMoletta, R. 1992. Control parameter variations in ananaerobic fluidised bed reactor subjected to organicshock loads. Wat. Sci. Tech. 25 (7) : 93-101.Neoh, C.H., Yahya, A., Adnan, R., Majid, Z.A. and Ibrahim,Z. 2013. Optimization of decolorization of palm oilmill effluent (POME) by growing cultures ofAspergillus fumigatus using response surfacemethodology, Environ. Sci. Pollut. Res. 20 (5) : 2912–2923.Ng, K.H., Cheng, Y.W., Khan, M.R. and Cheng, C.K. 2016.Optimization of photocatalytic degradation of palmoil mill effluent in UV/ZnO system based on responsesurface methodology. J. Environ. Manag. 184:487–493.Orhon, D., Tasli, R. and Sozen, S. 1998. Experimental basisof activated sludge treatment for industrialwastewaters-the state of the art. In: Fourthinternational symposium on waste management problemsin agreo-industries, 23-25 September 1998, Istanbul,Turkey.Qasim, S.R. 1999. Waste Water Treatment Plants – Planning,Anaerobic Fluidized Bed Reactor (AFBR) for the Treatment of High Solid Content Agro- 105Design & Operation. Second Edition, Technomic USA:413.Sutton, P.M. and Mishra, P.N. 1990. Biological fluidisedbeds for water & wastewater treatment: A state-of-the-art review. In: Proceedings of the 1990 waterpollution control federation conference, Washington D.C.Switzenbaum, M.S. 1983. A comparison of the anaerobicfilter and anaerobic expanded/fluidised bed process.Wat. Sci. Tech. 15 : 345-358.Tchobanoglous, G. and Burton, F.L. 1991. WastewaterEngineering Treatment, Disposal and Reuse. McGrawHill, Inc.Wong, P.W., Sulaiman, N.M., Nachiappan, M. andVaradaraj, B. 2002. Pre-treatment and membraneultrafiltration using treated palm oil mill effluent(POME). Songklanakarin J. Sci. Technol. 24 : 891-898.

Anaerobic Fluidized Bed Reactor (AFBR) for the

treatment of high solid content agro-industrial

wastewater

http://irep.iium.edu.my/92566/1/92566_Anaerobic%20Fluidized%20Bed%20Reactor.pdf

Anaerobic Fluidized Bed Reactor (AFBR) for the treatment of high solid content agro-industrial wastewater

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